DE102021006060A1 - Process and binder system for the production of components based on ceramics, metals and metal-ceramic composites using the binder jetting 3D process - Google Patents

Abstract

The invention relates to a method and binder system for the binder jetting 3D printing method for the production of components based on non-basic ceramics, metals or on the basis of metal-ceramic composite materials from the mixture of basic and acidic ceramics with metals.

Description

The invention relates to a method and binder system for the binder jetting 3D printing method for the production of components based on non-basic ceramics, metals or on the basis of metal-ceramic composites consisting of the mixture of basic and acidic ceramics with metals .

Binder jetting is an additive manufacturing process in which powdered starting material is bonded to a binder at selected points in order to create components. The process is standardized in the VDI guideline 3405 under the name "3D printing".

With 3D printing, the components are built up in layers. From 3D data z. B. on a height-adjustable table or with a higher-adjustable print head, a powder or granulate layer is applied and glued using a binder over the print head at the points that are part of the component geometry. Then z. B. lowered the table by one layer thickness and applied a new layer of powder. The excess powder is then returned for further use, the component is removed from the printer and powder residue is removed.

In the European specification 3210949 A1, a 3D binder jetting process is presented, which discloses a new binder system. The grain z. B. made of ceramic is coated with MgO and magnesium phosphate or a Sorel cement is added and a multi-nozzle system is used to apply water droplets to the coated grains, which cause a binding function. Binder levels above 20% are required to print a part with acceptable strength via this process using this binder system. The refractory expert knows that this high proportion of binder and also the chemistry of the binder system impairs the high-temperature properties, in particular the creep resistance, the corrosion resistance and the hot bending strength.

The invention is therefore based on the technical task of providing a binder and method for producing components for high-temperature applications using 3D printing.

In order to solve this technical problem, a binder system is disclosed in the present description which, due to its chemical composition and a required proportion of the binder of less than or equal to 10% by weight, can be used in the production of ceramics, metals and metal-ceramic composite materials for high-temperature applications using binder jetting 3D Printing method is operational. According to the invention, good high-temperature properties, in particular good creep resistance, good corrosion resistance and good hot bending strength at temperatures greater than 600° C., are made possible for the printed components in the first place.

Numerous patents disclose binders for setting ceramic, refractory products which are based on a reaction between a basic and an acidic binder component. Among other things, describes the DE 38 06 554 A 1 An anhydrous binder containing long chain fatty acids in conjunction with reactive MgO. In DE 29 51 502A1 the manufacture of foundry sand molds is disclosed. A carboxylic acid, a basic hydroxide and foundry sand are mixed in the presence of an aqueous solution of a carboxyl group-containing polymer. Based on the DE 691 14 412 T2 describes a carboxylic acid-containing material containing basic dolomite for use in a tundish, the dolomite being coated with a layer of calcium carbonate.

In the US 2005/0003189A1 describes a layer construction method for the production of models, in which a thermoplastic particulate material is mixed with a powdered binder and is printed in layers with an aqueous solvent. The binder should be easily soluble in the aqueous pressure medium. The models are then freed from the surrounding powder and, if necessary, dried in an oven in a post-process to increase their strength.

In WO 2014/056482 a 3D binder jetting process is disclosed which uses resin systems such as e.g. B. phenolic resin, furan, urea or amino resins, novolaks or resoles used as binders.

In the DE 102007032892 B4 discloses a basic, ceramic tundish mass which can be hardened by adding water and consists of a refractory base component and a binder system, with a binder component being an acidic component in the form of at least one acid and a second component is a basic component in the form of at least one base which reacts in an acid-base reaction upon addition of water to the tundish mass. Water is added to the basic tundish mass in a mixer, in particular, for example, in a compulsory mixer or a continuous mixer or in a spraying machine, for example a pressure tank spraying machine, in which the water is preferably added at the end of the hose.

The present invention relates to a multi-stage binder jetting 3D printing process for producing one or more shaped bodies based on non-basic ceramics, metals or on the basis of metal-ceramic composites from the mixture of basic and acidic ceramics with metals with good high-temperature properties, the method according to the invention comprising the steps: 1) Dry coating of the particle granules of the starting raw materials based on non-basic ceramics or metals or on the basis of metal-ceramic composites made of a mixture of basic and acidic ceramics with metals with a binder system made of a basic, ceramic Component with a proportion of less than or equal to 5% by weight and of an acidic solid component of less than or equal to 5% by weight in a mixer 2) layered construction of one or more shaped bodies by repeated application of the coated particle granules in the 3D printing process, 3) a pre-consolidation step with the targeted and selective drops of water through one or more computer-controlled nozzles to achieve pre-consolidation caused by a base-acid reaction between the coated granules of the shaped body, 4) an unpacking step, whereby the unsolidified particulate material is separated from the pre-consolidated shaped body and 5) the printed Shaped bodies over 400 °C in oxygen-containing or protected atmospheres, e.g. B. argon or heat-treated under vacuum and / or sintered, where 6) shaped bodies that have been sintered in protected atmospheres or under vacuum can be subsequently heat-treated in an oxygen-containing atmosphere above 400 ° C to passivation layers on the formation of oxides to generate.

According to the invention, basic-acid reactions for the production of components based on one or more non-basic ceramics, one or more metals or a mixture of ceramics and metals in the sense of metallo-ceramic composite materials for the binder jetting 3D process with targeted, selective drop-like addition of water via a controlled nozzle or via several controlled nozzles on coated granules with binder based on a basic binder component of magnesium oxide, dolomite, magnesium hydroxide, calcium hydroxide, aluminum hydroxide or magnesium-rich magnesium aluminate spinel or magnesium titanate, magnesium zirconate, calcium titanate or calcium zirconate or mixtures, and silicic acid, citric acid, amidosulfonic acid, Malic acid, tartaric acid, formic acid, acetic acid, boric acid are not disclosed as acidic components.

According to the invention, a basic-acid reaction for the production of components using binder jetting 3D printing methods based on one or more non-basic ceramics, one metal or more metals or from the mixture of ceramics and metals in the sense of metal-ceramic composites with a targeted, selective droplet-like addition of water via a controlled nozzle or via a plurality of controlled nozzles onto a layer of the materials already disclosed. According to the invention, these materials are already in an upstream treatment process with magnesium oxide, magnesium hydroxide, magnesium titanate, magnesium zirconate, aluminum hydroxide, magnesium-rich magnesium aluminate spinel, calcium oxide, calcium hydroxide, dolomite, calcium titatate, calcium zirconate or mixtures thereof as basic binder components, and silicic acid, citric acid, amidosulfonic acid, malic acid, tartaric acid, Formic acid, acetic acid, boric acid or mixtures thereof are dry-coated as the acidic component.

According to the invention, after the original shaping by means of the binder jetting 3D printing process, sintering takes place in air or in a protected atmosphere, e.g. B. under vacuum, argon, nitrogen etc.

According to the invention, a further heat treatment above 400° C. in an oxygen-containing atmosphere can take place after sintering in a protected atmosphere.

According to the invention, the magnesium-rich magnesium aluminate spinel has less than 70% aluminum oxide and is known on the market by way of example with the product name MR 66 with approx. 31% MgO and approx. 63% Al ₂ O ₃ from Almatis.

According to the invention, magnesium titanate, magnesium zirconate, calcium titanate or calcium zirconate also serve as sintering aids for better compaction during subsequent sintering both in pure ceramic components and in metal-ceramic molded components.

According to the invention are used as non-basic ceramics oxides such. B. alumina, silica, zirconia, titanium dioxide, alumina-rich magnesium aluminate spinel (alumina content greater than 70%), barium zirconate, lanthanum oxide, chromium oxide, lanthanum chromium or mixtures thereof, carbides such. B. silicon carbide, tungsten carbide, nitrides such. As silicon nitride, titanium nitride, aluminum nitride, boron nitride and borides such. B. titanium diboride.

According to the invention serves as non-basic ceramics carbon in all its modifications such. B. Graphite, carbon black, carbon nanotubes, carbon fiber etc.

Mixtures of oxides, nitrides, carbides or borides with or without carbon can also be used according to the invention, as premixed powders or as premixed and manufactured granules.

According to the invention metals from ferrous and non-ferrous metallurgy such. As steel, iron, aluminum, magnesium, copper, nickel, titanium, silicon, refractory metals such. B. molybdenum, tungsten, niobium, tantalum etc. or mixtures thereof. In these material combinations of metals and ceramics, basic ceramics such. B. magnesium oxide, magnesium oxide-rich magnesium aluminate spinel, calcium oxide or dolomite can be added.

Mixtures of metals with oxides, nitrides, carbides or borides with or without carbon can also be used according to the invention, as premixed powders or as premixed and prefabricated granules.

According to the binder system based on a basic ceramic and an acid, organic additives to increase the temporary strength such. B. polyvinyl alcohol (PVA) can be added.

According to the invention, fine-grained (less than 100 μm) or coarse-grained (more than 100 μm to 100 mm) starting powders based on metal or metals, oxide or oxides or combinations of both are used.

Two examples according to the invention follow: a) aluminum oxide (ceramic with the steps: dry pre-coating of the grains with the binder system according to the invention in the Eirich mixer, 3D printing using binder jetting 3D printing process, sintering at 1600° C. in an oxygen-containing atmosphere), and b) Steel and magnesium oxide (metal and basic MgO ceramic with the steps: granulation in the Eirich mixer, coating of the composite material granules with the binder system in the Eirich mixer, binder jetting 3D printing, sintering under argon at 1400 °C, heat treatment in an oxygen-containing Atmosphere, formation of oxide-containing passivation layers from the reaction of the steel and its alloying elements with the MgO, including in situ spinel formation).

example 1

Table 1 Material, including coarse grain Proportion [% by weight] _{Al2O3 3.15-2.5mm} 9.2 _{Al2O3 2.5-2.0mm} 6.9 _{Al2 O3} 2.0-1.25 mm 6.7 _{Al2O3 1.25-1.0mm} 1.9 Al ₂ O ₃ 1.0-0.63 mm 12.4 Material, of which medium grain _{Al2 O3} 0.63-0.315 mm 13.2 _{Al2 O3} 0.315-0.16 mm 7.0 Material, of which fine grain _Al2O3 < _0.16mm 43.4 Fine MgO 0-40 µm as basic binder component 5 Citric acid 0-40 µm as an acidic binder component 5

Dry mixing and coating of the aluminum oxide granules with 5% by weight MgO and 5% by weight citric acid takes place in an Eirich mixer. This is followed by 3D printing in a Desamanera binder jet printer machine, which has over 300 computer-controlled nozzles, which print cylinders of 50 mm in diameter and 25 mm in height based on a 3D printer code onto the grain mixture. The pre-consolidation step of the cylindrical molded component is caused by a base-acid reaction between the coated grains of the molded body with the targeted and selective dropping of water through one or more computer-controlled nozzles. Printing is followed by sintering in an electrically heated furnace with an oxygen-containing atmosphere at 1600° C. for 2 hours. This is followed by the strength determination using cold compressive strength. The strength is 12 MPa.

example 2

Table 2 below contains a mixture for the production of a slip, also referred to as a mixture, based on fine-grain steel 316 L, 5 to 50 μm and fine-grain MgO, 5 to 50 μm. Table 2 material Proportion [% by weight] MgO 40.0 Steel 316L 60.0 additive, thereof 0.5 Dolapix PC 75 (Zschimmer & Schwarz GmbH) 0.5 alcohol 40.0

Steel 316 L and MgO were filled into a mixing container to produce the slip. The average grain size of the steel was 10 μm, the average grain size of the MgO was 8 μm. In a further step, 0.5% by weight of the organic, alkali-free additive Dolapix PC 75 from Zschimmer & Schwarz was mixed with 40% by weight alcohol and added to the steel powder and the MgO. The mixture was then blended on a roller mill for 6 hours. The slurry thus obtained was poured into a gypsum mold to obtain moldings. After demoulding, the moldings were dried at 50° C. for 5 hours. The dried samples were pre-sintered in two stages under an argon atmosphere at a heating rate of 2 K/min, or else thermally pre-treated. The samples were first held at 850°C for 5 hours and then sintered at 1400°C for a holding time of 5 hours. The material obtained in this way was then broken up into various grain size classes in a cross-beating mill. Table 3 Material, including coarse grain Proportion [% by weight] Steel/MgO 3.15-2.5mm 9.2 Steel/MgO 2.5-2.0mm 6.9 Steel/MgO 2.0 -1.25 mm 6.7 Steel/MgO 1.25-1.0 mm 1.9 Steel/MgO 1.0-0.63mm 12.4 Material, of which medium grain Steel/MgO 0.63-0.315 mm 13.2 Steel/MgO 0.315-0.16 mm 7.0 Material, of which fine grain Steel/MgO < 0.16 mm 43.4 Fine MgO 0-40 µm as basic binder component 5 Citric acid 0-40 µm as an acidic binder component 5

The dry mixing and coating of the composite material grain based on steel 316 L/MgO from Table 3 with 5% by weight MgO and 5% by weight citric acid takes place in an Eirich mixer. This is followed by 3D printing in a Desamanera binder jetting printer machine, which has 340 computer-controlled nozzles, which print cylinders 50 mm in diameter and 25 mm in height based on a 3D printer code. The pre-consolidation step of the cylindrical molded component is caused by a base-acid reaction between the coated grains of the molded body with the targeted and selective dropping of water through one or more computer-controlled nozzles. After printing follows sintering in an electric furnace with graphite lining and in a protected argon atmosphere at 1400 °C for two hours. This is followed by the strength determination using cold compressive strength. The strength is 40 MPa. The cylindrical molded components based on steel 316 L and MgO, sintered under argon, are then heat-treated in an oxygen-containing atmosphere at 1000 °C for 30 minutes. This is followed by the strength determination using cold compressive strength. The strength is 50 MPa. As a result of this second heat treatment and the formation of passivation layers, the molded components have very good oxidation resistance and good high-temperature strength. The strength at 850 °C in an oxygen-containing atmosphere is in the range of 45 MPa.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 3806554 A [0007]
• DE 2951502 A1 [0007]
• DE 69114412 T2 [0007]
• US 2005/0003189 A1 [0008]
• WO 2014/056482 [0009]
• DE 102007032892 B4 [0010]

Claims (6)

Process using a binder for the production of components using the binder jetting 3D printing process, characterized in that for the production of one or more molded bodies based on non-basic ceramics, metals or based on metal-ceramic composites the mixture of basic and acidic ceramics with metals, the method comprises the steps 1) dry coating of the particle grains of the starting raw materials based on non-basic ceramics or metals or on the basis of metallo-ceramic composites from the mixture of basic and acidic ceramics with metals a binder system consisting of a basic, ceramic component with a proportion of less than or equal to 5% by weight and of an acidic solid component with a proportion of less than or equal to 5% by weight in a mixer, 2) layered construction of one or more shaped bodies by repeated application of the coated particle granules in the 3D printing process , 3) a pre-consolidation step with the targeted and selective drop of water applied through one or more computer-controlled nozzles to achieve a pre-consolidation caused by a base-acid reaction between the coated granules of the shaped body, 4) an unpacking step, wherein the non-solidified particulate material is removed from the pre-consolidated shaped bodies is separated and 5) the printed shaped bodies are heat treated above 400 °C and/or sintered in oxygen-containing or protected atmospheres, e.g. B. argon or under vacuum, where 6) moldings that have been sintered in protected atmospheres or under vacuum can be subsequently heat treated in an oxygen-containing atmosphere over 400 ° C to generate passivation layers through the formation of oxides. Binder for the production of components using the binder jetting 3D printing process claim 1 characterized in that the basic binder component is magnesium oxide, magnesium hydroxide, magnesium titanate, magnesium zirconate, aluminum hydroxide, magnesium-rich magnesium aluminate spinel with an aluminum oxide content of less than 70% by weight, calcium oxide, calcium hydroxide, dolomite, calcium titatate, calcium zirconate or mixtures thereof and the acidic component is silicic acid, citric acid , Sulfamic acid, malic acid, tartaric acid, formic acid, acetic acid, boric acid or mixtures thereof. Binder for the production of components using the binder jetting 3D printing process claim 1 and 2 characterized in that polyvinyl alcohol is added to the binder system consisting of a basic and an acidic component. Process and binder for the production of components using the binder jetting 3D printing process according to at least one of Claims 1 until 3 characterized in that the non-basic ceramics used are oxides such as aluminum oxide, silicon dioxide, zirconium dioxide, titanium dioxide, aluminum oxide-rich magnesium aluminate spinel with an aluminum oxide content greater than 70% by weight, barium zirconate, lanthanum oxide, chromium oxide, lanthanum chromium, carbides such as SiC, WC, nitrides such as silicon nitride, Titanium nitride, aluminum nitride, boron nitride, borides such as titanium diboride, carbon such as graphite, carbon black, carbon nanotubes, carbon fibers or mixtures thereof are used. Process and binder for the production of components using the binder jetting 3D printing process according to at least one of Claims 1 until 4 characterized in that the metals used are steel, iron, aluminum, magnesium, copper, nickel, titanium, silicon, refractory metals, molybdenum, tungsten, niobium, tantalum or mixtures thereof. Process and binder for the production of components using the binder jetting 3D printing process according to at least one of Claims 1 until 5 characterized in that basic ceramics such as magnesium hydroxide, magnesium oxide-rich magnesium aluminate spinel, calcium oxide, dolomite or mixtures thereof are used in the material combinations of metals and ceramics.